TeachingDemos (version 2.13)

TkListView: Interactivly view structures of list and list like objects.

Description

This is somewhat like the str function, except that it creates a new Tk window and a tree object representing the list or object. You can then click on the '+' signs to expand branches of the list to see what they contain.

Usage

TkListView(list)

Value

This function is ran for its side effects, it does not return anything of use.

Arguments

list

The list or object to be viewed.

Author

Greg Snow,

Details

This function opens a Tk window with a tree view of the list in the leftmost pane. Next to the tree is the result from the str function for each element of the list. Clicking on the '+' symbol next to list elements will expand the tree branch to show what that list/sublist contains. On the right is an output pane with 3 buttons below it. These can be used by first selecting (clicking on) a list element in the left pane (this can be a whole list or single element), then clicking on one of the buttons. The output from the button appears in the right pane (replacing anything that may have been there before). The 'print' button just prints the element/sublist selected. The 'str' button calls the str function on the selected element/list/sublist. The 'Eval:' button will evaluate the code in the entry box next to it with the selected element of the list being the 'x' variable. For example you could click on an element in the list that is a numeric vector, type 'hist(x)' in the entry box, and click on the 'Eval:' button to produce a histogram (current/default R graphics device) of the data in that element.

any lists/objects with attributes will show the attributes as an additional branch in the tree with a label of "<<attributes>>".

This function works on S3 objects that are stored as lists. Since currently S4 objects are saved as attributes, wrapping them in a list will work with this function to view their structure, see the example below.

See Also

str

Examples

if(interactive()) {
  tmp <- list( a=letters, b=list(1:10, 10:1), c=list( x=rnorm(100),
        z=data.frame(x=rnorm(10),y=rnorm(10))))
  TkListView(tmp)

  fit <- lm(Petal.Width ~ ., data=iris)
  TkListView(fit)


  if(require(stats4)){
   # this example is copied almost verbatim from ?mle
         x <- 0:10
     y <- c(26, 17, 13, 12, 20, 5, 9, 8, 5, 4, 8)
     ll <- function(ymax=15, xhalf=6)
         -sum(stats::dpois(y, lambda=ymax/(1+x/xhalf), log=TRUE))
     (fit <- mle(ll))
     TkListView(list(fit))
  }
}